Featured Research

Discovery of a new species of 213-million-year-old meat-eating dinosaur in New Mexico suggests the first dinosaurs wandered between parts of the Pangea supercontinent that later became North and South America, according to a team of researchers.

Share This

This is a fleshed-out reconstruction of the new Triassic carnivorous dinosaur Tawa hallae.

Credit: Jorge Gonzalez.

Did the first dinosaurs wander across continents or stay put where they first evolved? The first dinosaurs evolved 230 million years ago when the continents were assembled into one landmass called Pangea. The question of early dinosaur movements remained unclear until the discovery of some exciting new fossils.

Related Articles

In the Dec. 11, 2009, issue of Science, a team of paleontologists presents the 213-million-year-old fossils of previously unknown carnivorous dinosaur Tawa hallae, including several of the best preserved dinosaur skeletons from the Triassic Period.

Fossil bones of Tawa, named after the Hopi word for the Puebloan sun god, were recovered from a dig site in northern New Mexico known as Hayden Quarry. The quarry is located on Ghost Ranch, where late painter Georgia O'Keefe once lived. Fossil bones of several individuals were recovered, but the type specimen is a nearly complete skeleton of a juvenile that stood about 28 inches (70 centimeters) tall at the hips and was approximately 6 feet (about 2 meters) long, from snout to tail. Its body was about the size of a large dog, but with a much longer tail.

Based on an analysis of the relationships among Tawa and other early dinosaurs, the researchers hypothesize that dinosaurs originated in a part of Pangea that is now South America, diverging into theropods (like Tyrannosaurus rex), sauropodomorphs (like Apatosaurus) and ornithischians (like Triceratops); and then dispersed more than 220 million years ago across parts of Pangea that later became separate continents.

"This new dinosaur Tawa hallae changes our understanding of the relationships of early dinosaurs, and provides fantastic insight into the evolution of the skeleton of the first carnivorous dinosaurs" said Randall Irmis of the Utah Museum of Natural History and University of Utah, a co-author of the study.

In addition to Irmis, authors of the study included lead author Sterling Nesbit of the University of Texas at Austin; Nathan Smith of the University of Chicago and the Field Museum of Natural History; Alan Turner of Stony Brook University; Alex Downs of the Ruth Hall Museum of Paleontology in Abiquiu, N.M.; and Mark Norell of the American Museum of Natural History.

"If you have continents splitting apart, you get isolation," said Nesbitt. "So when barriers develop, you would expect that multiple carnivorous dinosaurs in a region should represent a closely related endemic radiation. But that is what we don't see in early dinosaur evolution."

Instead, the research team found three distinct carnivorous dinosaurs -- including the newly discovered Tawa -- in the fossil-rich, Late Triassic beds they investigated at Ghost Ranch. "When we analyzed the evolutionary relationships of these dinosaurs, we discovered that they were only distantly related, and that each species had close relatives in South America," said Irmis. "This implies that each carnivorous dinosaur species descended from a separate lineage before arriving in [the part of Pangea that is now] North America, instead of all evolving from a local ancestor."

At Ghost Ranch, the researchers found fossils from a carnivorous dinosaur related to Coelophysis, common to that region, and fossils from a carnivore closely related to Herrerasaurus, which lived in South America. The 6.6- to 13-foot-long (2- to 4-meter-long) skeletons of Tawa display characteristics that exist in both species and features found in neither, implying a separate lineage.

"The discovery of multiple dinosaur species in one place that emigrated from elsewhere got us wondering whether other Late Triassic reptiles show similar patterns" said Irmis. "It turns out a variety of other reptile groups made multiple trips from the northern and southern continents [then parts of Pangea] and back again during the Late Triassic, including other dinosaurs."

Because so many different groups with different life modes were able to move freely across Pangea, the research team concluded that during the Late Triassic, there were no major physical barriers, such as large mountain ranges, to the movement of reptiles between parts of Pangea that later separated into distinct continents.

But this presented a paradox to the team: "We wondered: if reptiles, including dinosaurs, were able to freely move around Pangea during the Late Triassic, then why aren't there any sauropodomorph and ornithischian dinosaurs in North America during the Triassic?" said Irmis. "Our conclusion is that climate, possibly related to latitude, controlled the distributions of some reptile species."

"We think that all the major dinosaur groups had the ability to get to North America [part of Pangea] during the Late Triassic, and may have even passed through, but for some reason, only the carnivorous dinosaurs found the North American climate to be hospitable during this time," concluded Irmis.

The first Tawa fossils were discovered in 2004 by volunteers taking a paleontology seminar at the Ruth Hall Museum of Paleontology in New Mexico. Museum scientists invited the team of paleontologists to come and take a look.

"The specimens are unusual because they are so well preserved," said Irmis. "Because dinosaur bones are hollow, they are usually broken and crushed, but those of Tawa are nearly pristine."

Irmis and the rest of the team began a full-scale excavation in 2006 and have continued to unearth new material every summer since then. The fossil bone bed extends for tens of yards along a hillside, promising many years of potential significant finds.

The research was supported by the National Science Foundation (NSF) through grants to Mark Norell, Alan Turner, Nathan Smith and NSF Graduate Research Fellowships to Sterling Nesbitt and Randall Irmis. The research was also featured in the NSF-funded IMAX 3-D movie "Dinosaurs Alive!"

Research was additionally sponsored by the National Geographic Society with other participating institutions including the University of Chicago, the Field Museum of Natural History, the University of Utah, Stony Brook University and the Ruth Hall Museum of Paleontology.

Featured Research

Mar. 3, 2015 — The precise dating of ancient charcoal found near a skull is helping reveal a unique period in prehistory. The Manot Cave, a natural limestone formation, had been sealed for some 15,000 years. It was ... full story

Mar. 2, 2015 — Richard III is the only male to be discovered at infamous former car-park site. A mysterious lead coffin found close to the site of Richard III's hastily dug grave at the Grey Friars friary has now ... full story

Mar. 1, 2015 — A study of how climate change has affected emperor penguins over the last 30,000 years found that only three populations may have survived during the last ice age, and that the Ross Sea in Antarctica ... full story

Feb. 27, 2015 — That swim tracks made by tetrapods occur in high numbers in deposits from the Early Triassic is well known. What is less clear is why the tracks are so abundant and well preserved. Paleontologists ... full story

Feb. 27, 2015 — DNA evidence shows surprise cultural connections between Britain and Europe 8,000 years ago. Researchers found evidence for a variety of wheat at a submerged archaeological site off the south coast ... full story

Feb. 26, 2015 — The miniweight boxing title of the animal world belongs to the mantis shrimp, a cigar-sized crustacean whose front claws can deliver an explosive 60-mile-per-hour blow akin to a bullet leaving the ... full story

Feb. 24, 2015 — Thirteen million years ago, as many as seven different species of crocodiles hunted in the swampy waters of what is now northeastern Peru, new research shows. This hyperdiverse assemblage, revealed ... full story

Feb. 24, 2015 — Tropical turtle fossils discovered in Wyoming reveal that when Earth got warmer, prehistoric turtles headed north. But if today's turtles try the same technique to cope with warming habitats, they ... full story

Feb. 24, 2015 — A French-Kenyan research team has just described a new fossil ancestor of today's hippo family. This discovery bridges a gap in the fossil record separating these animals from their closest ... full story

Feb. 24, 2015 — Climate-driven plague outbreaks in Asia were repeatedly transmitted over several centuries into southern European harbors, an international team of researchers has found. This finding contrasts the ... full story

Related Stories

Dec. 10, 2014 — Scientists have named the first definite horned dinosaur species from the Early Cretaceous in North America. The limited fossil record for neoceratopsian--or horned dinosaurs--from the Early ... full story

Mar. 5, 2014 — A new dinosaur species found in Portugal may be the largest land predator discovered in Europe, as well as one of the largest carnivorous dinosaurs from the Jurassic. T. gurneyi had blade-shaped ... full story

Jan. 7, 2014 — Dinosaur fossils are exceptionally rare in the Arabian Peninsula. Scientists have now uncovered the first record of dinosaurs from Saudi Arabia. What is now dry desert was once a beach littered with ... full story

Dec. 19, 2011 — For the first time, the presence of large bodied herbivorous dinosaurs in Antarctica has been recorded. Until now, remains of sauropoda had been recovered from all continental landmasses, except ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.